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Throttle Positioner

  1. When vacuum (V) is created below throttle plate upon deceleration, it becomes effective in chamber (A). This vacuum pulls diaphragm (7) to the left against pressure of spring (6).
  2. Valve (5), which is attached to diaphragm (7), opens allowing vacuum in chamber (A) to enter chamber (B) and pull diaphragm (2) to the right. This moves pull rod (1) and opens throttle plate via damper lever.
  3. When manifold vacuum decreases, spring (6) forces diaphragm (7) to the right, closing valve (5). This eliminates vacuum in chamber (B) allowing throttle return spring to force diaphragm (2) to the left.
  4. The altitude corrector (10) is installed with a slight preload and presses on valve (5). This preload will vary according to atmospheric pressure.
  5. When atmospheric pressure is low and manifold vacuum is reduced, the corresponding opening force by diaphragm (7) on valve (5) is also reduced. However, preload on altitude corrector (10) on valve (5) increases by the same amount. This makes sure that operation of throttle positioner is not affected by atmospheric pressure.
  6. Throttle positioner can be adjusted with adjusting screw (12), which is locked by a set screw (11).
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